In a typical photographic printer, a lamphouse is provided for projecting light of appropriate color and density through a photographic negative to expose the negative onto a photographic paper. A light sensor, such as a photocell, is disposed so as to measure the light projected through the negative, whereby to determine an appropriate exposure for the negative. The output of the light sensor is fed back, for example through an exposure control computer, to the lamphouse so as to control the light output of the lamphouse and provide a proper exposure of the negative. The lamphouse may include, for example, controllable colored filter paddles and/or attenuator wheels for providing the proper light output.
Certain features are required for the proper operation of such a printer. Separate from the lamphouse, a shutter mechanism is required for precisely controlling the timing of the exposure light. A neutral density filter is required, typically supported on its own controllable paddle, for selectively modifying the intensity of the light output by the lamphouse. A calibration filter is necessary for calibrating the response of the light sensor. This calibration filter is often provided in a negative size format for insertion into a negative gate by an operator. Alternatively, the calibration filter may be provided on a separately controllable paddle for selective introduction into the light path.
These features, i.e. the shutter mechanism, neutral density filter, and calibration filter, constitute a substantial amount of the space and technical complexity of the photographic printer.